Photographic transfer process utilizing the reducing action of a developer for producing a colored photographic transfer image



1957 E. H. LAND 2,802,735

PHOTOGRAPHIC TRANSFER PROCESS UTILIZING THE REDUCING ACTION OF A DEVELOPER FOR PRODUCING A COLORED PHOTOGRAPHIC TRANSFER IMAGE Original Filed on. a, 1946 Devclopoblc Phoi'osensifivc Maieriul lOa lOb 32/ I Q Phoiosensifive Layer He. NS? me D I R n eve oped Phcdosensrhvc Manna! Doveioper Scluiion Dcvdopcr Soiuhun I, y l U, H Image Carrying La er x lac: I21: 12: Unreqcfed Devcicper FIG. 4

Image Carrying Layer FIG.

- PhcfiosensiHve Layer v I ,4, fl V 5 so 32 Image Carrying Layer mwfi m gait/4 y United States Patent 0 PHOTOGRAPHIC TRANSFER PROCESS UTILiZlNG THE REDUCING ACTION OF A DEVELOPER FOR PRODUCING A COLORED PHGTDGRAPHIC TRANSFER IMAGE Edwin H. Land, Cambridge, Mass, assignor to Polaroid Corporation, Cambridge, Mass, a corporation of Delaware Original application October 8, 1346, Serial No. 762,039, now Patent No. 2,661,293, dated December 1, 1953. Divided and this application November it), 1953, Serial No. 391,189

12 Claims. (Cl. 9629) This invention relates to photography and, more particularly, to novel photographic processes.

This application is a division of my copending application Serial No. 702,039, filed October 8, 1946, for Process for Producing a Colored Photographic Image by Means of Exhaustion of Developer, now issued as U. S. Patent No. 2,661,293 on December I, 1953, which, in turn, is a continuation-impart of my application Serial No. 539,550, filed June 9, 1944, for Photographic Product, Process and Apparatus (abandoned and replaced by application Serial No. 64,870, filed December 11, 1948, now issued as Patout No. 2,543,181 on February 27, 1951).

It is a principal object of this invention to provide an improved photographic process wherein a visible positive image is obtained from a photosensitive layer containing a latent or developed negative image, by utilizing the differential effect created by said photosensitive layer on a substance, usable in forming said visible positive image, to control the amount of said substance which is available for creating said positive image.

Another object of the present invention is to provide a photographic process wherein a photosensitive layer containlng a latent or developed negative image is permeated with a substance having the capability of entering into a reaction which produces a visible effect on another layer, said substance is reacted with a material in said photosensitive laycr to selectively make portions of said substance incapable of creating said visible effect, and the remainder of said substance is used to create said visible effect on said other layer, said visible effect, due to its selective creation, forming a positive image.

Another object of the present invention is to assure, in processes of the above type, a substantially complete reaction of said substance with said material prior to the creation of said visible effect.

Another object of the invention is to provide a novel photographic process wherein a developer is reacted with a layer of photosensitive material containing a latent negative image to cause a development of said latent negative image and the portions of said developer which are not reacted by said photosensitive material during said development reaction are utilized in forming a positive image of said latent negative image in or on another layer.

Another object of the invention is to provide a positive image-forming reaction in a process of the above type wherein said unreacted and unoxidized portions of said developer are directly reacted with a coupler in a coupling reaction to provide a dye constituting a positive image.

Another object of the invention is to provide a positive image-forming reaction in a process of the above type wherein said unreaeted portions of said developer are utilized to reduce a nonphotosensitive reducible metallic salt to form a colored substance or pigment constituting a positive image.

Another object of the invention is to improve the contrast of a positive image produced in a process of the type described above by preventing migration of reacted 2 portions of said developer from said photosensitive layer to said other layer.

Other objects of the invention will in part be obvious and will in part appear hereinafter.

The invention accordingly comprises the process involving the several steps and the relation and order of one or more of such steps with respect to each of the others which are exemplified in the following detailed disclosure, and the scope of the application of which will be indicated in the claims.

For a fuller understanding of the nature and objects of the invention, reference should be had to the accompanying drawing wherein:

Figures 1 through 4 are diagrammatic representations of various steps of a preferred modification of the invention; Figure 1 showing a photosensitive layer containing a latent negative image; Fig. 2 showing the photosensitive layer after development; Fig. 3 showing an imagecarrying layer formed into a permeable assembly with the developed photosensitive layer; and Fig. 4 showing the final positive image on the image-carrying layer;

Fig. 5 is a diagrammatic cross-sectional view of a composite photographic film unit showing one physical embodiment of the invention;

Fig. 6 is a diagrammatic cross-sectional View of a composite photographic film unit showing another physical embodiment of the invention; and

Fig. 7 is a diagrammatic cross-sectional view of a composite photographic film unit showing still another physical embodiment of the invention.

in general this invention relates to novel photographic processes and products for the production of a fixed stable positive image of a latent or developed negative image contained in a photosensitive layer, the positive image being formed in or on another layer hereinafter referred to as an image-carrying layer.

A real image of any object is a visible likeness or reproduction of that object. Photographically, an image may be recorded in a photosensitive layer by transforming said layer, which is originally substantially homogenous throughout its volume, to a layer such that a chemical characteristic thereof has an imagewise variation throughout the image area, the variation being a function of the brightness aspects of the original subject image. The resulting record image may be a real image, i. e., a visible image, or a latent image, i. e., an image which, while not visible per se, has the capacity upon suitable chemical treatment to produce a visible image. The term record image, when used here in its photographic sense, may be characterized as a record of the brightness aspects of any predetermined subject matter such as a person, object, or real image, the record being in the form of a. layer of material of predetermined small thickness having throughout its image area an imagewise variation of a chemical characteristic of the layer, this chemical characteristic being capable of producing a visible contrast either by virtue of imparting different optical characteristics per se to said layer or by making possible the differential chemical treatment of said layer whereby differential optical characteristics are imparted to said layer.

This invention relates to the use of such a record image in a photosensitive layer for forming another image on an image-carrying layer, said other image being reversed in the positive-negative sense with respect to said record image.

In its preferred aspect the process involves the produc tion on an image-carrying layer of a positive image of a record negative image by permeating the layer containing said negative image with a uniform quantity of a substance in solution, selectively utilizing the differential chemical characteristic of said layer to produce an ellect on said uniformly permeated substance, said effect being the imagewise variation of said chemical transferring unaffected portions of said layer and utilizing said unaffected portions to create a varying visible effect which gives a positive image of said negative image.

The creation of the visible effect on the image-carrying layer may be the result of the creation of a color.

The first step of the preferred process is to permeate a uniform quantity of a liquid composition into the photosensitive layer containing a record image comprising a latent or developed negative image. The liquid composition preferably comprises a solution of a reactive substance. The latent or developed negative image in the photosensitive layer preferably comprises a photosensitive material having an imagewise distribution which varies as a direct function of the exposure creating said latent or developed negative image.

The amount of reactive substance permeating a unit area of the photosensitive layer is substantially uniform throughout an area thereof at least coextensive with said negative image and is preferably such that it will be substantially completely reacted by the portion of said photosensitive layer containing a highest concentration of said imagewise distributed material.

This reactive substance in the liquid compostion is one having the capability of entering into a reaction with said material in said photosensitive layer and also of entering into a reaction which produces a visible effect on said image-carrying layer.

In the next step of the process, the reactive substance is reacted with the material in the photosensitive layer and portions of said substance are rendered incapable of producing a visible effect as the result of this reaction. The extent of reaction between the substance and the material in the photosensitive layer preferably varies, from point to point thereof, as a function of the pointto-point degree of exposure creating the negative image. There thus remains a distribution of unreacted substance whose capability of creating a visible effect varies in amount from point to point.

As another step of the process, the remainder of the reactive substance, i. e., that portion thereof which did not react with the material in the photosensitive layer, is thereafter transferred to said imagecarrying layer from said photosensitive layer by superimposing one of said layers on the other of said layers, the superimposing being sufficiently intimate to permit the migration of said unreacted portions of said substance without any substantial degree of dispersion. The transferred unreacted portions of said substance are then utilized for creating a visible effect on said image-carrying layer. This visible effect preferably comprises the creation of a color and varies from point to point in accordance with the distribution of the unreacted substance. Due to the selective visible effect, i. e., color created, there is formed a positive image of said negative image on said image-carrying layer.

Referring now to Figs. 1 through 4 there is shown a diagrammatic representation of the various steps of a preferred embodiment of the process of the present invention.

Referring specifically to Fig. 1 there is provided a layer of photosensitive material 10, which is shown as having been exposed to a subject image to create developable portions indicated by the dots 16, these clots representing developable grains of photosensitive material. Various portions of the photosensitive layer have ditferent amounts of developable grains 16 therein, portion 10a having a maximum amount of developable grains, portion 10!) having substantially no developable grains, and the portion 100 having about half of its grains developable.

In Fig. 2, the photosensitive layer 10 is shown as having been uniformly permeated with a solution of the reactive substance. This permeation is such that there a function of characteristic, substance to said image-carrying exists a predetermined quantity per unit area of the substance distributed through the photosensitive layer 10. The uniform permeation is accomplished such as by dipping the photosensitive layer in a concentrated bath of the reactive substance, the photosensitive layer being in contact with the bath only long enough to absorb a predetermined quantity of the concentrated substance 14, either on its surface or within the layer 10. The photosensitive layer 10 should not be left in the bath long enough to permit the transfer of reacted portions of the substance from the layer 10 to the bath. The concentration of the bath should be so high that the photosensitive layer 10 may take up and support a uniform quantity of the substance, the concentration of the substance per unit area supported by the layer 10 being preferably just enough to be completely reacted by a most reactive portion of the photosensitive layer 10. Other methods of applying the solution of the substance to the photosensitive layer are equally feasible such as spreading a predetermined layer 14 of a viscous solution of the substance in contact with the surface of the photosensitive layer 10. The substance may also be applied by other means such as by spraying, etc.

After the solution has permeated the photosensitive layer 10, the reactive substance reacts with the developable portions 16. The distribution of one of the products of this reaction is indicated by the crosses 17, which may represent developed grains of photosensitive material. As can be seen, portion 10a of the photosensitive layer has a maximum amount of reaction product 17, portion 10b has substantially no reaction product 17, and portion has about half the amount of reaction product 17 as does the portion 100. Since the amount of reactive substance with which the photosensitive layer 10 is permeated is preferably so adjusted as to be no more than enough to be completely reacted by the most reactive portion of the photosensitive layer, there remains in the portion 10a no unreacted substance. In the portion 10b, there remains a maximum quantity of unreacted substance, and in the portion 10c, there remains a quantity of unreacted substance which is about half that remaining in the portion 10b. Thus, in this case, the amount of reacted substance is a direct function of the exposure and the amount of unreacted substance is an inverse function of the exposure creating the negative image.

Referring now to Fig. 3, the photosensitive layer 10 is shown as having been formed into a permeable unit with an image-carrying layer 12 by being superimposed on said image carrying layer in intimate relationship therewith such as in face-to-face contact. In this figure. the unreacted portions of the substance have migrated to the image-carrying layer 12, and exist within or on the surface of the image-carrying layer 12 in a quantity substantially inversely proportional to the amount of reaction of the substance in the corresponding portions of the photosensitive layer. In the portion 12a of the imagecarrying layer, which corresponds to the portion 10a of the protosensitive layer, there is substantially no unreacted substance on or within the surface of the image-carrying layer 12. In the portion 12b of the image-carrying layer there is a maximum amount of unreacted substance. In the portion 120, there is present about half the quantity of unreacted substance existing in the portion 12!]. Thus, where a maximum amount of reaction between the substance and the photo-sensitive layer 10 has taken place, there is available in the image-carrying layer a minimum amount of unreacted substance. On the other hand. where there is a minimum amount of reaction with the photosensitive layer 10, there is a maximum amount of unreacted substance available on the image-carrying layer. The portions of the substance which have reacted with the photosensitive layer 16 are preferably trapped within the photosensitive layer 10 so that no reacted substance migrates to the image-carrying layer in those portions where maximum reaction of the photosensitive layer has taken place. This trapping may be accomplished by a tanning action of the substance upon the gelatin, or other colloid of the photosensitive layer, or it may be due to the decreased molecular or ionic mobility of the reaction product of the reaction, or it may, Where the substance is a developer, be the result of coupling between the oxidized developer and a relatively immobile dye-forming component contained in the photosensitive layer, or in the viscous developer solution used in the processing. In this latter case the developer layer preferably adheres to the photosensitive layer. In some cases it is not essential that the reacted portions of the substance be trapped in the photosensitive layer or the viscous layer, but it is preferred that these reacted portions of the substance be kept away from the image-carrying layer, particularly where the reacted portions are capable of creating a color and thus spoiiing'the highlights and contrast of the positive image.

This selective distribution of the unreactcd portions of the substance on the image-carrying layer 12 is assisted, in a preferred embodiment, by the use of a highly concentrated solution of the reactive substance and by superimposing the adjacent surfaces of the photosensitive layer and the image-carrying layer 12 in intimate relationship during this transfer. Such an arrangement prevents any substantial dispersion of the reactive substance in its migration from the photosensitive layer to the imagecarrying layer.

The image in unreacted substance which exists on or within the surface of the image-carrying layer 12 is next utilized to form a visible image, preferably by the creation of a color on or within the surface of the imagecarrying layer 12. This color may be created by the formation of a pigment or by the formation of a dye, the intensity of color created being dependent upon the amount of substance available for the color-creating reaction.

In Fig. 4 the final positive image is shown as being composed of a number of colored points, schematically represented at 19, which may be color-created by a pigment, such as a colloidal metal, or which may be color-created by molecules of dye. For simplicity of description, the colored points 19 are represented as having an intensity depending on depth, while actually the intensity of color may be primarily at and near the surface of the imagecarrying layer, the effect depending upon the intensity of dye created, the size of a pigment created, or the quantity per unit area of color created. In the portion 12a of the imagecarrying layer where no unreacted substance existed, there is no formation of a color. In portion 12b,

there is produced a maximum intensity of color, and in portion 12c, there is produced a color having about half the intensity of the color produced in the portion 12b. It can be seen, then, that there is thus produced a color which selectively varies from point to point, throughout the area of the image-carrying layer 12, substantially in inverse proportion to the amount of reacted photosensitive material in the corresponding portions of the photosensitive layer 10.

Where the image on the image-carrying layer 12 is formed in terms of a pigment 19 and the reactive substance comprises a developer, the unreacted portions of the developer may be used to form this pigment 19 by the reducing action of the developer on a reducible metallic salt. This reducible metallic salt can be a salt which is negligibly photosensitive such as mercurous chloride or a photosensitive salt such as a silver halide. In either case, the pigment formation is selective, due to the selective reduction of the salt, varying from point to point, and being a minimum where there was a maximum development of the latent negative image and being a maximum where there was a minimum development of the latent negative image. There is thus created on the imagecarrying layer a positive pigment image of the latent nc aivc image in the photo-sensitive layer.

When the reactive substance is a developer and a dye image is formed on the image-carrier layer 12, there are a number of ways of accomplishing the dye formation, depending upon the type of developer utilized. In one method, there may be provided, for reaction with the unreacted portions of the developer, a color-former capable of coupling with these unreacted, i. e., unoxidized, portions of the developer to create a color 19. This color, due to its selective creation, varies in amount from point to point, being a minimum 'where there was a maximum development of the latent negative image, and being a maximum where there was a minimum development of the latent negative image. There is thus created, on the image-carrying layer 12, a positive dye image of the latent negative image in the photosensitive layer.

In another method of forming a dye image there is utilized, to create a color, a color-former capable of coupling with oxidized, rather than unoxidized, portions of the developer. In this case, the developer is reacted with the photosensitive material containing a latent negative image to cause a development of the negative image resulting in a selective oxidation of the developer and a trapping of the oxidized developer within the developed portions of the photosensitive layer 10, it being necessary to prevent migration of the oxidized developer from the photosensitive layer 10. The remainder of the developer is then utilized to create a color 19 on the image-carrying layer 12. In order to form this color, it is necessary to oxidize these unreacted portions of the developer, after the selective reaction of the developer with the latent negative image. This oxidation may be accomplished by providing an oxidizing agent on the image-carrying layer, in which case the oxidizing agent may be either a photosensitive material such as a silver halide or a monophotosensitive oxidizing agent such as sodium perborate. It is also contemplated to oxidize the unreacted portions of the developer on the image-carrying layer by aerial oxidation which may be carried out by separating the imagecarrying layer from the photosensitive layer whereby to permit the ready access of oxygen from the atmosphere to the unreacted portions of the developer. After the developer has been oxidized on the image-carrying layer it is reacted with a suitable color-former to cause a coupling and the creation of a color, the concentration and distribution of which varies from point to point substantially in inverse proportion to the amount of development in corresponding portions of the latent negative image.

In both of the above methods of dye image formation, the color-former, which is reacted with the developer to cause a coupling therebetween, is preferably located on the image-carrying layer 12 in solid form. It may, however, be coated on, or included in, the photosensitive layer 10, or it may be, in some cases, included in solution in the liquid composition. This latter modification of the invention is particularly feasible where the developer is coated on one of the layers in solid form rather than being in solution in the liquid composition.

In still another method of forming a dye image, a selfcoupling developer is used. This developer may be one of the type known in the art as a direct color-forming developer, i. e., one which couple with itself when oxidized. The developer is selectively reacted with the photosensitive material containing a latent negative image, and the reacted portions are preferably trapped in the photosensitive layer. Then the unreacted portions of the developer are utilized to selectively create a color 19 on the image carrying layer 12, by oxidizing the unreacted portions of the developer.

A preferred method of permeating the photosensitive layer with a uniform quantity per unit area of a liquid composition containing the reactive substance is to release the liquid composition between the photosensitive layer and the image-carrying layer and to spread this liquid composition in a uniform thin layer between the photosensitive layer and the image-carrying layer. Such a 7 method of uniform permeation has certain advantages and is particularly adaptable for use with film units of the type shown in Figs. 5, 6 and 7 which show preferred examples of the physical embodiments of the present invention.

Each of these film units may be processed by the application thereto of a single mechanical stress to cause the release and spreading of the liquid composition, thus making possible the processing of the film unit either within a hand camera, or as the result of ejection of the film unit from a hand camera.

The construction of the film unit also permits accurate spreading of the liquid composition in a uniform thin layer in a position to permeate the photosensitive layer with a uniform amount of a solution of the reactive substance.

Since the liquid composition is spread between two layers, which may be only slowly permeable to oxygen, it substantially prevents the access of oxygen to the liquid composition during the time it exists in a layer form within the confines of the film unit. This arrangement prevents the aerial oxidation of the reactive substance, where such a substance is oxidizable. Separation of the image-carrying layer from the film unit renders the surrounding atmosphere available for effecting the aerial oxidation of oxidizable material on the image-carrying layer. This feature permits the use of reactive substances which are quite easily oxidized and prevents such oxidation until the positive image has formed, or until it is desired to oxidize the reactive substance for the purpose of creating a positive image.

When the outer surface of the layers of the film unit are opaque to actinic light, the construction of the film unit permits the liquid composition, particularly Where the liquid is viscous, to form a lightproof laminate of the film unit so that the film unit may be ejected from a camera into daylight immediately after the mechanical treatment. Exposure of the photosensitive layer is effected prior to the formation of said lightproof laminate and with the photosensitive and the image-carrying layers in spread apart or separated relation with respect to each other. Since the composite laminate is opaque to actinic light, the photographic process may be carried to completion outside of the camera with no danger of destroying the latent image as the result of light reaching the photosensitive material.

Such film units should have certain features in order that they may fulfill the requirements of the process. In the first place, it is preferable that the film units have within their confines all the materials necessary for the com plete processing thereof to produce the final positive image. In the second place, the film units should be so designed that they may inherently assure the proper sequence of reactions, or can be so used as to assure this proper sequence of reactions.

The physical embodiment of the broad invention, shown in Figs. 5, 6 and 7, generally involves a composite film unit comprising a photosensitive layer, an image-carrying layer and a container for a liquid composition, the container being positioned in the film unit for release of its liquid composition so as to permit the permeation of the liquid into at least the surface portions of the photosensitive and image-carrying layers. The liquid composition is preferably viscous and preferably includes the reactive substance, and at least includes a solvent therefor.

The film unit of Fig. preferably comprises a photosensitive layer 30, an image-carrying layer 32, and a container 34 having therein a liquid composition and positioned to release its liquid between the two layers 30 and 32. For supporting the photosensitive layer 30 there is provided a usual film base 36.

In another physical embodiment of the invention, shown in Fig. 6, there is provided a film unit of the general type described in connection with the discussion of Fig. 5, the

embodiment of Fig. 6 being particularly useful in those processes described previously where the reactive substance reacts with a material on the image-carrying layer to create a color.

Referring now to Fig. 6, where like numbers correspond to like elements of Fig. 5, there is provided the usual layer 30 of photosensitive material, carried by a base layer 36. An image-carrying layer 32 is also provided. On that surface of the image-carrying layer 32 which is closest to the photosensitive layer 30 there is provided a coating or layer 38 of a material which is only slowly permeable to a liquid composition within a container 34.

In general the embodiment of the invention of Fig. 6 is usable with all processes of the type discussed previously and is particularly useful for those processes wherein a developer is the reactive substance and the imagecarrying layer 32 contains a material Which is quite reactive with the developer, the reaction of the developer with the material being that which creates a color constituting the positive image.

In still another physical embodiment of the invention there is provided a composite film unit comprising a pho tosensitive layer and an image-carrying layer similar to the embodiment of Figs. 5 and 6 but having its various layers so arranged with respect to the introduction of the liquid composition that the liquid composition must permeate through the layer of photosensitive material before reaching the image-carrying layer. Such an embodiment of the invention is shown in Fig. 7 where like numbers correspond to like elements of Figs. 5 and 6.

Referring specifically to Fig. 7 there is provided a usual photosensitive layer 30 coated on the upper surface of an image-carrying layer 32. A container 34 is provided in the film unit in a position to discharge its liquid composition adjacent that surface of the photosensitive layer 30 which is farthest from the image-carrying layer 32. For assisting in spreading the liquid composition in a uniform thin layer adjacent the surface of the photosensitive layer 30 there is provided a relatively impermeable backing layer 40.

The embodiment of Fig. 7 may be utilized with any of the processes previously described and it has particular advantage in those processes wherein the reaction of the reactive substance with the negative must be completed before the liquid composition permeates the image-carrying layer.

In the above-described processes portions of a reactive substance, such as a developer, are selectively rendered incapable of creating a color by reaction with a layer of photosensitive material containing a latent negative image to cause the development thereof, and the unreacted portions of the reactive substance are utilized in a color-creating reaction to form a positive image on an image-carrying layer. In such processes it is essential to carry the first reaction to substantial completion before the second reaction commences. The proper sequence of the two reactions is obtainable in numerous ways.

One way of obtaining the proper sequence is described above in connection with the discussion of Figs. 1 through 4, where the development of the latent negative image is accomplished while it is separate from the locale of the second reaction, i. e., before it is formed into a permeable assembly with the image-carrying layer 12. This way of assuring the proper sequence between the two reactions is not as preferred as these ways to be discussed hereinafter, since it is not particularly adaptable for use with a compact apparatus such as a hand camera.

When film units of the type of Figs. 5, 6 and 7 are utilized with the process of the present invention and the liquid composition is spread in a uniform layer within the film unit while the various layers thereof are in permeable relationship to each other, the proper sequence of reactions may be assured by providing the proper physical and/or chemical relationship between the various materials.

There are a number of forms that this relationship may take. The first form, which is particularly useful with the embodiment of Fig. 5, involves the provision of materials such that the development of the latent negative image is inherently faster than the color-creating re.- action which forms the positive image. An example of this modification of the invention is one wherein the silver halide in the latent negative image is more readily reducible than the metallic salt on the imagecarrying layer. Another modification of this form of the invention, useful with the embodiment of Fig. 5, involves the provision of an oxidizing agent on the imagecarrying layer which oxidizes the developer more slowly than the developer develops the latent negative image.

Another form of a relationship of material for assuring the proper sequence of reactions is the provision of some means for temporarily preventing the color creating reaction. This means may comprise a coating, as shown in Fig. 6, on the surface of the image-carrying layer or a hardened surface on the image-carrying layer which is adapted to retard penetration of the developer into the image-carrying layer until such time as the developer has been selectively reacted by the latent negative image in the photosensitive layer. Materials suitable for such a coating, as will appear in the more detailed exam? ples which illustrate the invention, comprise polyvinyl alcohol, cellulose nitrate and the like.

Another way of assuring the proper sequence of reactions is to provide a process, particularly useful with the embodiment of Fig. wherein the image-carrying layer must be subjected to a definite treatment before the unreacted developer, on its surface, may enter into the color creation reaction. In one form of this modification of the invention there is provided, on the image-carrying layer, a layer of unexposed photosensitive material. In this case, the unreacted developer cannot reduce this unexposed photosensitive material until it has been made developable by exposure to light. In another form, where there is used a developer which, when oxidized, couples with itself or another substance, this coupling can be prevented, if no oxidizing agent is included on or within the image carrying layer, or if the oxidizing agent must be treated, such as by exposure to light, before it is capable of oxidizing the unreacted portions of the developer. In this case, the developer cannot couple until the image-carrying layer has been exposed to aerial oxidation or the oxidizing agent has been activated such as by being exposed to actinic light.

Still another way of assuring the proper sequence of reactions, as shown in Fig. 7, is to adjust the direction of permeation of the developer so that it permeates through, and is substantially completely reacted by, the photosensitive layer before reaching the image-carrying layer.

In the above discussion of the processes applicable to Figs. 1 through 4 and Figs. 5, 6 and 7, no mention is made of the preferred materials. These materials vary in accordance with the specific processes involved and are discussed in more detail hereinafter.

In the following discussion of preferred examples of the various processes of the present invention it may be assumed that all the processes may be practiced as shown in Figs. 1 through 4 and are usable with the modifications of the physical embodiments of the invention shown in Figs. 6 and 7, by suitably arranging the reactive material on the image-carrying layer and either supplying a protective slowly permeable coating thereover or causing the reactive substance to permeate through the photosensitive layer before it contacts the reactive material. Where the process is also particularly well suited for use with a film unit of the type shown in Fig. 5, it is so stated. In the following examples the numbers refer to Figs. 1

a 10 through 4 unless the process is particularly applicable to one of Figs. 5 through 7.

One method of creating a dye positive image from a latent negative image is to use on the image-carrying layer a material capable of coupling with unreacted portions of a reactive substance, such as a developer, to form a dye. This dye may be formed by the use of a colorformer, or dye base such as a diazonium fast salt, on the image-carrying layer, which is capable of coupling with unreacted portions of an amine or phenol developer. Such a process is set forth in the following non-limiting example:

Example] The image-carrying layer 12, which may be conventional baryta coated paper, is prepared by coating with a water solution of Naphthosol Fast Orange Salt GC and allowed to dry. Naphthosol Fast Orange Salt GC is stabilized and diazotized meta chlor aniline (American Dyestutf Reporter, 1939, vol. 28, No. 4, pp. 82-83). The photosensitive layer 10 comprises a relatively slow, high contrast orthochromatic silver halide emulsion, such as is employed with copying film, commonly known to the trade as contrast process ortho film. The photosensitive layer is exposed to actinic light and permeated with a developer by dipping for a few seconds in a solution of 1,5-dihydrnxynaphthalene. Development of the photosensitive layer is continued for several minutes after removal from the developer bath. The developed photosensitive layer is then placed in contact with the imagecarrying layer to cause the unreacted portions of the developer to migrate to the surface of the image-carrying layer where they couple with the Naphthosol Fast Orange Salt GC to form a positive dye image on the imagecarrying layer. This image appears to be intensified by the aerial oxidation of the unreacted developer after the initial positive image is formed. Thus the image appears to be formed by the unreacted portions of the developer which couples, partially in its unoxidized and partially in its oxidized condition, with the color-forme1z Those portions of the developer oxidized as the result of the development of the latent negative image appear to be trapped within the photosensitive layer and thus cannot spoil the positive image.

In another method of forming a dye positive image from a latent negative image there is utilized a colorformer capable of coupling with oxidized, rather than unoxidized, portions of the developer. Such a process where the color-former is contained in the liquid is de scribed in the following non-limiting example:

Example 2 The photosensitive layer 10, which may comprise an orthochrornatic emulsion of the character described in connection with Example 1, is exposed to actinic light to create therein a latent negative image. This latent negative image is developed using the following developer:

Diethylparaphenylenediamine hydrochloride grams 6 Sodium sulphite do 10 Potassium bromide do 0.5 Sodium carbonate do 117 Color-former (p-nitrophenylacetonitrile) do 0.10 Water cc 2000 Acetone cc- 10 Example 3 A cyan positive image may be obtained in Example 2 by using, as the color-former, 2,4-dichloro-1-naphthol.

Example 4 A yellow positive image may be obtained, in Example 2, by using, as the color-former, ethyl acetoacetic acid.

While the above description of the invention relates to a process where the color-former is included in the developer liquid, it is equally possible to swab a solution of one or more of the color-formers on the image-carrying layer. This swabbing with a color-former may be accomplished either before or after the unreacted portions of the developer have been transferred to the image-carrying layer. In this case the developer solution is the same except that no color-former is included therein.

In the above specific example, sodium perborate was used as the oxidizing agent for oxidizing those portions of the developer unreacted by the development of the latent negative image. Other non-photosensitive oxidizing agents such as sodium perchlorate, ammonium dichromate, and ammonium persulfate may also be used.

It is also contemplated to use a photosensitive oxidizing agent on or within the surface of the image-carrying layer. Such a photosensitive material can be a silver halide and is preferably dispersed within the surface of the paper. This photosensitive material can be either exposed or unexposed depending upon the desired type of process. If exposed, it reacts with the developer as soon as it contacts the developer. If unexposed, it must be exposed to actinic light, or otherwise made developable, before it can oxidize the developer. This latter condition has certain advantages since it enables the use of such an unexposed oxidizing agent with a film unit of the type shown in Fig. 5.

In practicing the above modification of the invention it is equally possible to rely on aerial oxidation as the sole means for oxidizing the unreacted portions of the developer as set forth in the following example:

Example The process of Example 2 is modified by eliminating the oxidizing agent from the image-carrying layer 12. When the image-carrying layer has been imbibed with the developed negative for 4 or 5 minutes it is separated therefrom and the invisible image in unreacted developer on the surface of the image-carrying layer is exposed to aerial oxidation. As the developer oxidizes it couples with the color-former to create a color and thus produces a positive image.

In the process of the type of Example 2, where a colorformer couples with the oxidized developer, it is desirable to insure the trapping, within the photosensitive layer, of all the developer that is oxidized by the development of the latent negative image. Such a trapping may be improved by including within the photosensitive layer a colorformer that couples with the oxidized developer to form a relatively immobile dye. Thus, as the developer is oxidized by the development of the latent negative image, it immediately couples with the color-former in the photosensitive layer 10 and is converted into an immobile dye, thereby being trapped within the photosensitive layer. This is particularly desirable where the color-former used to create the positive image is placed on the image-carrying layer rather than in the developer solution.

In still another method of forming a dye positive image from a latent negative image, a self-coupling developer is used. This developer may be one of the type known in the art as a direct color-forming developer, 1. e., one which couples with itself to form a dye when oxidized, as set forth in the following nonlimiting examples:

Example 6 A layer of silver halide photosensitive film 30-36 of Fig. 5, such as orthochromatic copying film of the type described in Example 1, is exposed to a subject image. A preferred form of image-carrying layer 32 comprises a sheet of imbibition paper. A suitable liquid composition contains the following materials:

With such a liquid composition, the process is preferably carried out by spreading a thin layer of the liquid composition between the exposed photosensitive layer 30 and the image-carrying layer 32. This spreading may be accomplished by releasing the liquid composition from a container 34 positioned between these two layers and spreading the liquid by means such as a pair of pressure rollers. The 1,5-dihydroxynaphthalene develops the latent negative image and, where development occurs, it self couples to form an immobile dye. Where development does not occur, the unreacted developer migrates to the surface of the image-carrying layer. The image-carrying layer 32, with the positive image in terms of unreacted developer on its surface, is then separated from the photosensitive layer 30 and exposed to air so as to oxidize the unreacted developer. This oxidation causes the developer on the image-carrying layer to self-couple, thus creating a color and forming a positive image of the subject image.

It is equally possible to use oxidizing agents on the image-carrying layer of Example 6 rather than relying on aerial oxidation to oxidize the unreacted deveolper on the image-carrying layer. In such a case the film unit should be of the form of Fig. 6 or 7 and the oxidizing agents may be of the various types discussed in connection with Examples 2 through 4 above.

Where the positive image on the image-carrying layer is formed in terms of a color created by a pigment, as distinguished from a color created by a dye, the unreacted portions of the developer may be used to form this pigment by the reducing action of the developer on a reducible salt, as set forth in the following nonlimiting example:

Water cc. Sodium earboxymethyl cellulose "grams-.. Sodium hydroxide do 1,5 -dihydroxynaphthalene do Example 7 The layer 10 of photosensitive material preferably com prises an orthochromatic emulsion of the copying film type referred to in Example 1. The layer 10 is exposed to actinic light to create therein a latent negative image. This negative image is then developed by placing it in a bath containing:

Grams Hydroquinone 25.2 Sodium sulphite 37.8 Sodium hydroxide 36.1 Water 900 The layer 10 is removed from the bath after about 30 seconds and development is allowed to continue for about 2 minutes. The developed negative image, containing an invisible image in unreacted developer, is then placed in intimate contact with an image-carrying layer comprising a sheet of uniformly exposed photosensitive paper such as a relatively fast, conventional enlarging paper having an emulsion comprising silver bromide and silver chloride. The unreacted developer permeates and develops the exposed photosensitive grains in the imagecarrying layer and thus develops a positive image in silver on the image-carrying layer. The undeveloped grains in 13 the image-carrying layers are then preferably fixed out by bathing in a suitable silver halide solvent, such as a solution of sodium thiosulphate.

The process of Example 7 has been described in connection with a process of the type shown in Figs. 1 through 4. It may equally be used in film units of the type shown in Figs. 6 and 7, or inra film unit like Fig. where the image-carrying layer is suflicicntly impermeable so as to delay permeation thereof by the developer. If it is desired to include a silver halide solvent in the liquid composition for the purpose of removing unreduced silver halide from the image-carrying layer of Example 7 the photosensitive material in the photosensitive layer is made of less soluble material than the silver halide in the image-carrying layer. The unreduced silver halide may be removed from the image-receiving layer to a protective colloid film formed between the image-carrying layer and the photosensitive layer by a plastic material such as sodium carboxymethyl cellulose carried in the liquidprocessing composition or this unreduced silver halide may be transported to the base which supports the photosensitive layer.

In still another modification of the invention, a nonphotosensitive salt is added to the image-carrying layer for the purpose of making available a material which can be reduced to a pigment by unreacted portions of the developer. This salt may be added after the invisible image in unreacted developer has been formed on the surface of the image-carrying layer. One method of practicing this feature of the invention is set forth in the following nonlimiting example:

Example 8 A copying film. of the type heretofore described, is used asthe photosensitive layer 10, and a sheet of imbibition paper is used as the image-carrying layer 12. The photosensitive layer is then exposed to a subject image and developed with a liquid composition 14 crmprising a mixture of solutions A and B as follows:

Water to make 390 grams.

This development is preferably accomplished by spreading the liquid composition in a uniform thin layer between the photosensitive layer 36 and the image-carrying layer 32 of Fig. 5. This spreading is preferably accomplished by releasing the liquid composition from a container 34 therefor positioned between the two layers. After several minutes the image-carrying layer 32 is separated from the photosensitive layer 30 and there is seen an extremely faint yellowish image, which apparently is an image in unreacted developer which has started to oxidize. The image-carrying layer 32 is next swabbed with a dilute solution of silver nitrate and a gray positive image is developed as the result of the reduction of the silver nitrate by the unreacted developer.

Example 9 A yellow positive image can be obtained in the process of Example 8 by swabbing the image-carrying layer 32, containing an invisible positive image in unreacted developer, with a salt such as ferric chloride, chromic trioxide or platinum chloride.

In another modification of the invention wherein unreacted portions of the developer are utilized for creating a color in terms of a pigment, a nonphotosensitive salt is a 14 selectively reduced to colloidal particles by these unreacter portions of the developer, as set forth in'the follow ing example: Example 10 An image-carrying layer 32 of Fig. 5 is formed of baryta paper and is prepared by swabbing with a 2% solution of chloroplatinic acid. The photosensitive layer 30 and the base layer 36 may comprise a sheet of Contrast Process Ortho film. With such materials the liquid composition in the container 34 preferably comprises:

Water "cc" 476 Sodium sulphite grarns 9 Sodium hydroxide do 19.6 Sodium carboxymethyl cellulose do 42.6 Hydroquinone do- 9 The film unit is processed by exposing the photosensitive layer 30 to actinic light and then passing it through a Wringer. The layers are kept together for a few minutes and then separated to reveal a yellow positive image on the image-carrying layer.

Example 11 An image-carrying layer 32 of Fig. 5 is formed of baryta paper and is prepared by swabbing with a 2% solution of palladium chloride. The photosensitive layer 30 and the base layer 36 may comprise a sheet of the heretofore described copying film. With such materials the liquid composition in the container 34 preferably The film unit is processed by exposing the photosensitive layer 30 to actinic light and then passing it through a wringer. The layers are kept together for a few minutes and then separated to reveal a yellow positive image on the image-carrying layer.

Example 12 The contrast of the positive image obtained by the process of Example 11 may be improved by treating the prepared image-carrying layer with (a) ammonium hydroxide or (b) ammonium hydroxide and hydrochloric acid to form colorless palladium complexes in place of the palladium chloride.

Other reducible salts, which may be nonphotosensitive or only slightly photosensitive, such as a silver salt of sodium earboxyrnethyl cellulose, may also be used as the reducible metallic salt on the image-carrying layer 32.

Another modification of the invention wherein the reaction of the developer with the negative image is inherently faster than the color-forming reaction is described in the following nonlimiting example:

Example 13 The photosensitive layer 30 and the base layer 36 of Fig. 5' may comprise a silver halide photographic film such as the heretofore described copying film. For use with this photosensitive layer 30 the liquid composition in the container 34 preferably comprises:

The image-carrying layer 32 is preferably formed of a sheet of baryta paper which has been swabbed with a color-former capable of coupling with unreacted portions of the pyrocatechin. Such a color-former may be applied by making an alcohol and water solution of Naphthosol Fast Orange Salt GC. The photosensitive layer 30 is exposed to actinic light, and the developer is then spread between the exposed photosensitive layer 30 and the image-carrying layer 32 by the use of pressure rollers or other suitable means. The pyrocatechin appears to react first with the latent negative image in the photosensitive layer 30, and then the unreacted portions thereof migrate to the image-carrying layer where they couple with the color-former on the image-carrying layer to give a positive image.

In still another modification of the embodiment of Fig. wherein a dye positive image is obtained, a process is used which is similar to that described in Example 2. In the following example there is shown a method of practicing this feature of the invention with the modification of Fig. 5 wherein the proper sequence of reactions is assured by using an oxidizing agent which oxidizes the developer more slowly than the developer develops the latent negative image:

Example 14 The photosensitive layer 30 and the base layer 36 preferably comprise a sheet of the coyping film of the preceding examples, and the image-carrying layer 32 comprises a sheet of baryta paper which has been swabbed with a solution of sodium perborate. A preferred liquid composition comprises:

After exposure of the photosensitive layer to actinic light to create therein a latent negative image, the film unit is processed to release the liquid composition from the container 34 and to spread the liquid in a uniform thin layer between the photosensitive layer 30 and the imagecarrying layer 32. The developer (diethylparaphenylenediamine hydrochloride) develops the latent negative image and, where development occurs, it couples with the colorformer and apparently is trapped within the negative by forming a relatively immobile dye. The unreacted portions of the developer are then slowly oxidized by the sodium perborate on the image-carrying layer. As these portions are oxidized they couple with the color-former to create a color on the image-carrying layer constituting the positive image.

A specific modification of the embodiment of Fig. 6 is described in the following nonlimiting example wherein a metallic salt is selectively reduced by unreacted portions of a developer and a slowly permeable polyvinyl alcohol coating is placed over the metallic salt to assure a proper sequence of reactions.

Example A solution is prepared by adding grams of mercurous nitrate to 200 cc. of a 3 percent nitric acid solution. A sheet of baryta paper, for use as the image-carrying layer 32, is placed in this solution for two minutes and the excess solution is removed from the sheet by the use of a squeegee. The sheet is then soaked in a 10 percent solution of sodium chloride for two minutes, thus forming mercurous chloride in the surface of the baryta paper. The sheet is then dried in air at room temperature. To one surface of sheet prepared as above there is laminated a layer 38 of polyvinyl alcohol. This layer 38 of polyvinyl. alcohol is preferably in the neighborhood of .0006 inch thick and is laminated to the baryta sheet by using a water solution of polyvinyl alcohol.

For use with the above described composite sheet 32-38 a liquid composition in the container 34 preferably comprises the following ingredients:

Grams Water 1860 Sodium carboxymethyl cellulose 116 Sodium sulphite 78 Sodium hydroxide 74.6 Citric acid 38.5 Hydroquinone 52 In preparing this liquid composition, the water and sodium carboxymethyl cellulose are mixed for two hours. Then all of the other elements, except the hydroquinone, are added and mixed for 5 minutes. Lastly the hydroquinone is added and the whole batch is mixed for two hours at 50 C. under an atmosphere of nitrogen.

For the negative photosensitive layer 3036 a preferred material is a sheet of the previously mentioned copying film. The photosensitive layer 30 is exposed to a subject image and the film unit is processed, as by passing it through a pair of pressure rollers to release the liquid composition from the container 34 and to spread the liquid in a uniform thin layer between the photosensitive layer 30 and the polyvinyl alcohol coating 38. When the above described liquid composition is spread between the exposed photosensitive layer 30 and the polyvinyl alco hol coating 38 on the image-carrying layer 34, the developer develops the latent negative image in the photosensitive layer, this development being substantially completed before any substantial permeation of the polyvinyl alcohol layer 38 takes place. Where the developer is unreacted by this development, it permeates through the polyvinyl alcohol coating and reduces the mercurous chloride on the surface of the image-carrying layer to colloidal black particles forming a positive image of the latent negative image.

While the above modification of the invention describes a preferred form thereof, numerous other materials and processes may be utilized. The slowly permeable layer 38 may comprise plastics other than polyvinyl alcohol, and reducible salts other than mercurous chloride may be used. The liquid composition is also susceptible of wide variations without departing from the scope of the invention.

While the slowly permeable layer 38 of polyvinyl alcohol is preferably applied in the form of a sheet by laminating to the image-carrying layer, it is equally possible to cast, from an aqueous solution, a layer 38 of polyvinyl alcohol directly on the surface of the prepared imagecarrying layer 32 by the use of a doctor blade or other coating techniques.

The slowly permeable barrier layer 38 may equally be formed of a plastic such as cellulose nitrate, as set forth in the following example:

Example 16 In this case a sheet of baryta paper, containing mercurous chloride, is dipped in a bath containing a 2% one-half second cellulose nitrate solution in equal parts of butyl alcohol and butyl acetate. The sheet is dried, and the layer of cellulose nitrate is found to be approximately .0001 to .0002 inch thick over the mercurous chloride. Such a sheet is preferably used with a developer of the type mentioned above.

In the embodiment of the invention of Figs. 5, 6 and 7, the material which reacts with the developer on the image-carrying layer 32 may be situated on the surface thereof nearest the photosensitive layer. If such be the case with respect to Fig. 7, the photosensitive layer 30 is preferably so formed that it may be readily separated from the image-carrying layer 32. This separation may be assisted by including within the liquid composition a film-forming material, such as sodium carboxymethyl cellulose, which is capable of forming a strong adhesive bond between the photosensitive layer 30 and the backing layer 40. Thus when the imagecarrying layer 32 is separated from the backing layer 40, the photosensitive layer 30 adheres to the backing 17 layer 40. The photosensitive layer of Fig. 7 may, if desired, be carried by a suitable permeable base material such as a sheet of gelatin, in which case the base can be mounted with respect to the image-carrying layer so as to be readily separable therefrom as in the manner of conventional stripping film.

In another modification of Figs. 5, 6 and 7, the material which reacts with the unreacted portions of the developer is situated on the surface of the image-carrying layer farthest from the photosensitive layer. In this case no separation of the various layers of the film unit is required in order to view the positive image.

Visibility of the negative image, in instances where the layers of the film unit are to remain unseparated after positive image formation, may be prevented by the use of a suitable opaque material, for example baryta paper, for the image-carrying layer.

In still another medification of the embodiment of Figs. 5, 6 and 7 there may be one reactive material on one surface of the image-carrying layer and another reactive material on the other surface of the image-carrying layer. As an example of such an arrangement, as applied to Fig. 7, an oxidizing agent may be included on the upper surface of the image-carrying layer in a position to oxidize unreacted portions of the developer as it permeates through the composite film unit. n the lower surface of the image-carrying layer there may be a color-former capable of coupling with the oxidized developer. As the developer reaches the color-former on the lower surface it couples therewith to form a positive dye image.

In the physical embodiments of the invention represented by Figs. 5, 6 and 7, the container 34 preferably comprises a paper-backed metal foil coated on its inner surface with a resin, such as polyvinyl butyral, which is inert to alkalies, although it may take numerous other forms.

The liquil composition in the container 34 preferably comprises an aqueous solution of the reactive substance. For assisting in spreading the liquid in a uniform film, the liquid preferably includes a viscosity-increasing compound constituting a film-forming material of the type which, when spread over a water-absorbent base, will form a relatively fiim, dimensionally stable film. Where the aqueous solution is alkaline, the film-forming material is preferably one which is not hydrolyzed in an alkaline solution. A preferred film-forming material is a high molecular weight polymer as, for example, a polymeric, water-soluble ether inert to an alkali solution, such as hydroxyethyl cellulose or a metal salt of carboxymethyl cellulose, e. g., sodium or aluminum carboxymethyi cellulose. Other film-forming materials or thickening agents can be used for the conversion of nonviscous solutions to viscous solutions where the conditions are such that their ability to increase the viscosity of the solution is not destroyed when left in solution for a considerable length of time. The viscosity of the liquid composition is preferably in the neighborhood of 20,000 centipoises although it may be as low as 8 centipoises. The high viscosities are preferred, since they give a more accurate control of spreading of the liquid composition.

In the various physical embodiments of the invention, the liquid composition in the container 34 preferably comprises an aqueous solution of the reactive substance. In some cases, however, it is desirable to include the reactive substanoe, such as a developer, in or on one of the layers of the film unit and for the liquid composition to include only water, possibly an alkali, and possibly a film-forming material to aid in accurate spreading. In other cases, the liquid composition may, for example, comprise only an aqueous solution of the developer, and there may be included in solid form in one of the layers of the film unit any alkali which may be required.

In still another modification of the physical embodiment of the invention the film unit may contain no liquid and may contain, in solid form, all of the various materials ordinarily carried in solution within the film unit. Such a modification of the invention is not as preferred as those described, since it requires the addition of a solvent to the film unit and thus cannot be processed by the mere application of mechanical stress to the film unit. Such a modification of the invention is, however, included within the scope of the present application.

The image-carrying layer, while being preferably formed of papers such as those known in the art as baryta paper or imbibition paper, may be formed of numerous other materials such as a water-permeable plastic or a water-permeable, reversible, film-forming organic colloid capable of having high viscosity characteristics and appreciable jelly strength, in which dye bases or salts may be suspended.

Examples of other suitable image-carrying layers are regenerated cellulose; poiyhydroxy alkanes, such as polyvinyl alcohol; sodium alginate; cellulose ethers, such as methyl cellulose, or their derivatives, such as sodium carboxymethyl cellulose or hydroxyethyl cellulose; papers; proteins, such as glue or gelatin; carbohydrates, such as gums and. starch; and mixtures of these materials where the latter are compatible. Where the above materials are transparent they may be mounted on an opaque base if desired, or have incorporated therein a colloidal pigment to render them opaque.

Throughout the specification and appended claims the expression positive image has been used. This expression should not be interpreted in a restrictive sense since it is used primarily for purposes of illustration, in that it defines the image produced on the image-carrying layer as being reversed, in the positive-negative sense, with respect to the image in the photosensitive layer. As an example of an alternative meaning for positive image, assume that the photo-sensitive layer is exposed to actinic light through a negative transparency. In this case the latent image in the photosensitive layer will be a positive and the image produced on the image-carrying layer will be a negative. The expression positive image is intended to cover such an image produced on the image-carrying layer.

In preceding portions of the specification the expression color has been frequently used. This expression is intended to include the use of three colors to obtain black.

Throughout the specification and claims the expression superimposing has been used. This expression is intended to cover the arrangement of two layers in overlying relation to each other either in face-to-face contact or in separated condition and including between them at least one layer or stratum of a material which may be a viscous liquid.

Since certain changes may be made in the above process without departing from the scope of the invention herein involved, it is intended that all matter contained in the above description or shown in the accompanying drawing shall be interpreted as illustrative and not in a limiting sense.

What is claimed is:

l. A process of forming positive transfer images in color wherein a single application of liquid to an exposed silver halide emulsion containing a latent image produces the necessary sequences of reaction for giving a finished positive transfer print, said process comprising the steps of: permeating said exposed silver halide emulsion with a liquid composition, and, during said permeation, having said emulsion so superposed on an image-receiving material that said liquid has access to said image-receiving material; providing within the lamination comprising said emulsion and said image-receiving material a silver halide developer and a substantially nonphotosensitive salt capable of reacting with unoxidized developer to give a colored reaction product; said nonphotosensitive salt being selected from the group consisting of diazonium salts, mercury salts, iron salts, chromium salts, platinum salts and palladium salts; said salts being located within said image-receiving material substantially to the exclusion of said developer and said developer being located in the remaining portion of said laminat on substantially to the exclusion of said salt, said developer and said salt being dissolvable in said liquid and so distributed throughout the portion of said lamination in which they are respectively located as to have a substantially uniform concentration per unit surface area of said lamination; said de veloper being present per each said unit area substantially only in such quantity as to be substantially completely reacted in fully exposed unit areas of said emulsion; at least said developer being mobile in said lamination when dissolved in said liquid; developing said latent image by means of said developer and thereby causing said developer to become oxidized in proportion to the development of exposed silver halide for each said unit area of said emulsion, developer so oxidized becoming exhausted and unavailable for reaction with said salt; said development also providing an imagewise distribution of unoxidized developer; transferring at least a portion of said imagewise distribution of unoxidized developer to said image-receiving material; and reacting said transferred, unoxidized developer with said salt to impart to said image-receving material a visible, colored, reversed mage of the developed image.

2. A process of forming positive images in color as defined in claim 1, including the step of separating said image-receiving material and said emulsion from their superposed relationship at some stage of said process after said unoxidized developer has been transferred to said image-receiving material.

3. A process of forming transfer images in color as defined in claim 1, wherein said developer is contained in said liquid composition when said liquid composition is permeated into said silver halide emulison.

4. A process of forming transfer images in color as defined in claim 1, wherein said developer is contained in said liquid composition and said image-receiving ma terial is part of a separate element, and including the step of retarding contact of said liquid composition with said image-receiving material by causing said liquid composition, before coming into contact with said image-receiving material, to pass through a stratum of material located between said emulsion and said image-receiving material, said stratum of material being characterized by being slowly permeable to said liquid composition.

5. A process of forming transfer images in color as defined in claim 1, wherein the permeation of said emulsion with said liquid composition is eliected by the step of providing a layerwise distribution of said liquid composition between said emulsion and another element supporting said image-receiving material.

6. A process of forming positive transfer images in color as defined in claim 5, including the step of separating said image-receiving material and said photosensitive element from their superposed relationship at some stage of said process after said imagewise distribution of unoxidized developer has been transferred to said imagereceiving material.

7. A process of forming positive transfer images in color as defined in claim 1, including the steps of providing a layerwise distribution of liquid composition having said developer dissolved therein between said emulsion and a stratum of material which is located on said imagereceiving material and is characterized by being less permeable to said liquid composition than is said emulsion, and permeating said emulsion with liquid composition from said layerwise distribution while retarding contact of liquid composition with said image-receiving material until said liquid composition has passed through said stratum of lesser permeability.

8. A process of forming transfer images in color as defined in claim 1, wherein said nonphotosensitive salt is substantially uniformly distributed throughout at least a stratum of said image-receiving material adjacent the surface of said material to which said imagewise distribution of unoxidized developer is transferred.

9. A process of forming positive transfer images in color as defined in claim 1, wherein said nonphotosensitive salt is a substantially nonphotosensitive diazonium salt directly reactable in a coupling reaction with said unoxidized developer to form a dye.

10. A process of forming positive transfer images in color as defined in claim 9, wherein said developer is contained in said liquid composition when said liquid composition is permeated into said silver halide emulsion.

11. A process of forming positive transfer images in color as defined in claim 1, wherein said nonphotosensitive salt is a reducible, substantially nonphotosensitive mercury salt which in reduced form is a colored substance.

12. A process of forming positive transfer images in color as defined in claim 11, wherein said developer is directly reactable in a reducing reaction with said mercury salt and is contained in said liquid composition when said liquid composition is permeated into said silver halide emulsion.

References Cited in the file of this patent UNITED STATES PATENTS 2,661,293 Land Dec. 1, 1953 FOREIGN PATENTS 716,428 France Oct. 6, X931 OTHER REFERENCES Ricketts: British Journal of Photography, June 5, 1914, page 446. 

1. A PROCESS OF FORMING POSITIVE TRANSFER IMAGES IN COLOR WHEREIN A SINGLE APPLICATION OF LIQUID TO AN EXPOSED SILVER HALIDE EMULSION CONTAINING A LATENT IMAGE PRODUCES THE NECESSARY SEQUENCES OF THE REACTION FOR GIVING A FINISHED POSITIVE TRANSFER PRINT, SAID PROCESS COMPRISING THE STEPS OF PERMEATING SAID EXPOSED SILVER HALIDE EMULSION WITH A LIQUID COMPOSITION, AND, DURING SAID PERMEATION, HAVING SAID EMULSION SO SUPERPOSED ON AN IMAGE-RECEIVING MATERIAL THAT SAID LIQUID HAS ACCESS TO SAID IMAGE-RECEIVING MATERIAL; PROVIDING WITHIN THE LAMINATION COMPRISING SAID EMULSION AND SAID IMAGE-RECEIVING MATERIAL A SILVER HALIDE DEVELOPER AND A SUBSTANTIALLY NONPHOTOSENSISTIVE SALT CAPABLE OF REACTING WITH UNOXIDIZED DEVELOPER TO GIVE A COLORED REACTION PRODUCT; SAID NONOPHOTOSENSITIVE SALT BEING SELECTED FROM THE GROUP CONSISTING OF DIAZONIUM SALTS, MERCURY SALTS, IRON SALTS, CHROMIUM SALTS, PLATIUM SALTS AND PALLADIUM SALTS; SAID SALTS BEING LOCATED WITHIN SAID IMAGE-RECEIVING MATERIAL SUBSTANTIALLY TO THE EXCLUSION OF SAID DEVELOPER AND SAID DEVELOPER BEING LOCATED IN THE REMAINING PORTION OF SAID LAMINATION SUBSTANTIALLY TO THE EXCLUSION OF SAID SALT, SAID DEVELOPER AND SAID SALT BEING DISSOLVABLE IN SAID LIQUID AND SO DISTRIBUTED THROUGHTOUT THE PORTION OF SAID LAMINATION IN WHICH THEY ARE RESPECTIVELY LOCATED AS TO HAVE A SUBSTANTIALLY UNIFORM CONCENTRATION PER UNIT SURFACE AREA OF SAID LAMINATION; SAID DEVELOPER BEING PRESENT PER EACH SAID UNIT AREA SUBSTANTIALLY ONLY IN SUCH QUANTITY AS TO BE SUBSTANTIALLY COMPLETELY REACTED IN FULLY EXPOSED UNIT AREAS OF SAID EMULSION; AT LEAST SAID DEVELOPER BEING MOBILE IN SAID LAMINATION WHEN DISSOLVED IN SAID LIQUID; DEVELOPING SAID LATENT IMAGE BY MEANS OF SAID DEVELOPER AND THEREBY CAUSING SAID DEVELOPER TO BECOME OXIDIZED IN PROPORTION TO THE DEVELOPMENT OF EXPOSE SILVER HALIDE FOR EACH SAID UNIT AREA OF SAID EMULSION, DEVELOPER SO OXIDIZED BECOMING EXHAUSTED AND UNAVAILABLE FOR REACTION WITH SAID SALT; SAID DEVELOPMENT ALSO PROVIDING AN IMAGEWISE DISTRIBUTION OF UNOXIDIZED DEVELOPER; TRANSFERRING AT LEAST A PORTION OF SAID IMAGEWISE DISTRIBUTION OF UNOXIDIZED DEVELOPER TO SAID IMAGE-RECEIVING MATERIAL; AND REACTING SAID TRANSFERRED, UNOXIDIZED DEVELOPER WITH SAID SALT TO IMPART TO SAID IMAGE-RECEVING MATERIAL A VISIBLE, COLORED, REVERSED MAGE OF THE VELOPED IMAGE. 